https://www.jasongaylord.com/blog/2020/11/06/type-namespace-record-init-could-not-be-found

I was recently working with Hot Chocolate and used the new C# 9.0 record types. At the time, I still had an older version of .NET 5.0 installed. When compiling, I was receiving the following error:

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error CS0246: The type or namespace name 'record' could not be found (are you missing a using directive or assembly reference?)

The type or namespace name 'record' could not be found (are you missing a using directive or assembly reference?

I also notice the following exception when debugging in VS Code:

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Predefined type 'System.Runtime.CompilerServices.IsExternalInit' is not defined or imported

Predefined type 'System.Runtime.CompilerServices.IsExternalInit' is not defined or imported

This lead me to search for this error online. During an earlier build of .NET 5.0, both the record type as well as init setters were accidentally unavailable as the IsExternalInit class was set as static instead of sealed. This is explained in issue 37763. Luckily, by removing the old .NET 5.0 SDK and installing the new version solved this issue.